Non-ferrous metals other than steel material (iron and alloy containing mainly iron) are becoming highly useful in industry; and an amount of a non-ferrous metal to be used is increasing. In order to avoid resource depletion of the non-ferrous metals, recycle technique which effectively utilizes non-ferrous metals contained in wastes such as home electric appliances is becoming highly important. For example, rare metal or rare noble metal is recovered from parts of wasted mobile phones, personal computers, automobiles and the like, which is sometimes called urban mines and intensely studied.
For recovering rare metal or rare noble metal, a recovery method using a chemical reaction, a recovery method using solvent extraction, and the like have been conventionally proposed. For example, JP-A 2010-150569 discloses a method for producing a platinum group element metal powder, comprising chlorinating waste material containing a platinum group element in a molten salt bath to form a metal chloride, and then subjecting the resulting metal chloride to reduction treatment to obtain metal powder having high purity. In the method, chlorine gas is blown into the molten salt bath and reacted at a temperature of 300 to 1000° C., whereby a chloride of a metal to be recovered is formed. Accordingly, a recovery method using a chemical reaction has a problem that consumption of a large amount of energy is accompanied. Further, there is also a problem that the cost of constructing a recovery system is necessary.
As the recovery method using solvent extraction, JP-A 2007-270250 discloses, as a method of selectively recovering a platinum group metal from an aqueous solution, a procedure of back-extracting palladium with an aqueous ammonia solution, and crystallizing palladium from the palladium-containing aqueous ammonia solution. The solvent extraction method has an advantage that, even when a concentration of a metal component is low, the metal component can be recovered. On the other hand, it is necessary to use a large amount of various solvents such as an organic solvent. For this reason, there is a problem that a large amount of waste solvent is generated and an environmental load is great.
JP-A 2008-127604 describes use of a biological membrane, such as an egg shell membrane, in a method of recovering a noble metal. The recovery method, however, needs an electric reduction recovery method, such as a gold electrolysis method, and has a different configuration from that of the method of the present invention.